Combine import statements for same module

Also move `$imports` to end per convention.

src/sidebar/util/test/oauth-client-test.js

 import fetchMock from 'fetch-mock';
 import sinon from 'sinon';
 
-import { $imports, TokenError } from '../oauth-client';
-import OAuthClient from '../oauth-client';
-
 import FakeWindow from '../../test/fake-window';
+import OAuthClient, { TokenError, $imports } from '../oauth-client';
 
 const fixtures = {
   tokenResponse: {